The Irish shareholders of the business could earn a further $100 million if the business meets certain sales targets.

Narcan is a nasal spray used to revive people who have overdosed on opioids. It is a market leader in the United States, where it is carried by law enforcement officers in several states.

The single dose spray, which contains the chemical naloxone hydrochloride – is the only FDA approved needle-free emergency opioid overdose treatment.

Addiction to opioids – mainly prescription painkillers, heroin and fentanyl – has emerged as a serious public health crisis in the United States, especially in rural areas.

According to the US Centers For Disease Control And Prevention, the epidemic claimed over 70,000 lives last year. The US surgeon general released a public health advisory earlier this year urging more Americans to carry naloxone.

Maryland group Emergent BioSolutions said on Tuesday it would buy the Irish business to beef up its portfolio of treatments for public health threats.

US President Donald Trump in March declared the addiction crisis a public health emergency in October at an event where he introduced Adapt Pharma executive, Mike Kelly and said he wanted to give first responders access to life-saving drugs that can reverse overdoses.

Emergent’s shares were up marginally in after-hours trading on Tuesday, while those of Opiant Pharmaceuticals, Adapt’s commercial partner, jumped nearly 42 per cent.

Emergent said it had “no plans to change” Narcan’s pricing and would maintain the 40 per cent discount available to state and local governments and non-profit organisations.

The transaction involves Emergent paying $635 million in cash and shares to Adapt’s six executive shareholders. The further $100 million cash payment is linked to hitting sales milestones between now and the end of 2022, 2022, Emergent said. – Additional reporting Reuters